Recent BaBar Results on $B$ Decays Page: 2 of 6
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where GF is the Fermi constant, mB and m1 are the B+ and T meson masses, fB
is the B meson decay constant and TB is the B+ lifetime.
The B+ - T+v decay is challenging because the final state contains two or
more neutrinos. It lacks the usual signal B mass and beam energy constraints to
reduce continuum and mis-reconstructed B background. To combat this we use the
"recoil" method. The T(4S) resonance produces two B mesons and we reconstruct
fully or partially the other B meson, called the "tag" B. This is done using the
common decays B- -> D0l-vX0 (semi-leptonic tag) and B- - D0(*)X- (hadronic
tag). The remaining particles are attributed to the signal B meson. Results for the
semileptonic6 and hadronic7 tag approaches from BABAR are shown in Table 1.
Table 1. B+ -+ T+v branching fractions.
B+ -T+v Branching fraction (10-4) Significance (fBIVibI) 10-4
Semi-leptonic 0.9 + 0.6 + 0.1 1.3 7.2.8 + 0.2
Hadronic 1.8+0 8 0.4 0.2 2.2 10.1+
Combined 1.2 + 0.4 + 0.3 + 0.2 2.6 -
These results are consistent with the first evidence seen by the Belle and provide
constraints on the SM19 (see Fig.1). B+ - T+v is sensitive to possible intermediate
charged Higgs bosons2 4. Exclusion regions (95% CL) for this new physics scenario
are shown in Fig. 1.1.5
B > v --- -
0.58
F--r constrait from B K~and Am
.1s5 ' 2
1 .05 0 0.5 1 115 2
Pi500
j 450
a 400
z350
250
200
150
100
50
0LEP Direct Search Limit
1020 3040 06 0 80 901 0
tangFig. 1. Constraints from B+ i T+v on the Standard Model p - q plane (left) and exclusion
regions for tan/3 vs charged Higgs mass from B+ _ +v (right).
3. Measurement of IVubi
A key goal of the B factories is to over-constrain the SM flavour sector. The dom-
inant constraint comes from sin 2). To over-constrain, and thus test the SM, IVm I
should be measured as precisely as possible and compared to that from the SM fit.B -U+v (World Avg, 2007)
-4
. m fCi-t
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Clark, P.J. & U., /Edinburgh. Recent BaBar Results on $B$ Decays, article, November 15, 2011; United States. (https://digital.library.unt.edu/ark:/67531/metadc840081/m1/2/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.